According to the National Sleep Foundation, sleep happens in cycles that repeat themselves about every 90 minutes. The first stage, which is called N1, includes falling asleep and light sleep. N2 is the onset of sleep when your breathing becomes regular, you detach from your surroundings, and your body temperature drops. N3 is the deepest and more restorative phase of sleep when growth hormone is released, blood pressure drops, and your breathing slows. REM starts about 90 minutes after falling asleep and recurs throughout the night. During this phase, your eyes dart back and forth, your brain is engaged, and you dream.

11.
You know when you're drifting off and all of a sudden you're yanked awake by the sensation that you're falling? These are called sleep starts. What is the more technical term for this phenomenon?

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Hypnic jerks

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Parasomnias

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Cerebral jumps

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Hypnotic jerks

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None of the above

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Hypnic jerks

Sleep starts are also known as hypnic jerks. They occur when you're drifting off to sleep and are simply involuntary muscle twitches in your arms, legs, or other parts of your body. It's not clear why they happen, although there are some theories, like the idea that as you fall asleep your brain misunderstands your muscles relaxing as a signal that you're falling and responds by tensing your muscles to protect you during impact.

12.
Going without sleep for _______ hours could impair you about as much as someone with a BAC of .05 (aka mild impairment) from alcohol. For reference, the legal limit for driving in all 50 states is .08.

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9-11

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11-13

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13-15

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15-17

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17-19

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19-21

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21-23

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Wrong!

17-19

A small 2000 study found that subjects who were awake for 17-19 hours performed tasks involving reaction time, vigilance, hand-eye coordination, and more about as well as (or worse than) people with a BAC of .05 after drinking alcohol.